As well as PIE outperformance, the corporate and provisional tax-take also beat Treasury predictions.

“The bulk of these positive variances is expected to persist through to the end of June,” the Treasury report says.

Introduced in 2007 in conjunction with KiwiSaver, the PIE regime helped breathe new life into New Zealand’s stagnant retail funds industry. As well as removing a tax impediment for investing in pooled vehicles, the PIE rules introduced an incentive for fund investors – particularly those on the highest marginal rate – with the top rate set at 28 per cent.

Just prior to the arrival of KiwiSaver and PIE, total retail funds under management (FUM) in New Zealand languished under $20 billion and falling. According to a Morningstar NZ market share report, as at December last year of the roughly $53 billion retail it measured, over $50 billion was invested via PIEs, split between KiwiSaver ($24.8 billion) and non-KiwiSaver ($28.5 billion) products.

(A recent Plan for Life survey, put the March 31, 2015 NZ retail FUM at $62.6 billion with KiwiSaver accounting for $28.5 billion of the total.)

According to the 2014 Financial Markets Authority (FMA) annual KiwiSaver report, the government raked in about $150 million in PIE tax on FUM of about $21.4 billion.

KiwiSaver subsidies were forecast to cost the government $882 million in the 12 months to June 30, the Treasury 11-month financial statements show.

In total, Treasury reported an operating balance surplus of $4.6 billion over the period in question, which was “$4.5 billion stronger than forecast”.

As well as the higher-than-predicted tax revenue, the government accounts recorded “net gains on financial instruments” of almost $6.3 billion or “$558 million higher than forecast”.

“Net losses on non-financial instruments were $3.0 billion lower than forecast, mainly due to lower than forecast actuarial losses on the ACC claims liability, mostly reflecting the impact of higher interest rates on discount rates and changes in inflation assumptions,” the Treasury document says.